LAGOS , Nigeria -LRB- CNN -RRB- -- The imprisoned leader of the Nigerian militant group MEND has accepted an unconditional amnesty offer from the government , his lawyer said Friday .

`` The president has ordered his release , and we are hoping he will be released very soon , '' Wilson Ajuwaand said , referring to his client , Henry Okah . `` We have briefed him on the amnesty and are now working out the details . ''

CNN could not independently verify the lawyer 's information , and Nigerian President Umaru Yar ` Adua could not be reached for comment .

Yar ` Adua made the amnesty offer to Okah in June .

Okah , who had been MEND 's main arms smuggler , was arrested in September 2007 in the Angolan capital , Luanda . He was later extradited to Nigeria and has been in prison since then .

`` We support Henry Okah 's decision to accept any deal that will ensure his early release to attend to his failing health under the current circumstances , '' said Jomo Gbomo , a MEND spokesman . `` Since he has no weapons to surrender , the deal should be a straightforward one . ''

An International Crisis Group report in April about the conflict between government forces and militants in the oil-rich Niger Delta said Okah is accused of treason , terrorism and kidnapping . His lawyers and relatives say he needs kidney treatment not available in Nigeria , the report said .

MEND has declared an `` all-out war '' on the government , demanding a fairer distribution of oil wealth in the Niger Delta . The group wants oil revenue reinvested in the region instead of enriching those the militants consider corrupt politicians . Many of MEND 's attacks have been aimed at oil and gas installations in the region .

Okah 's release had been a key demand of MEND before they accept any government amnesty offer .

After receiving news of Okah 's acceptance of the government officer , MEND issued a statement .

`` The recent appointment of Mr. Timi Alaibe as the special adviser to the president on Niger Delta-Nigeria-MEND-Amnesty affairs by the Nigerian government is a humble and welcome development that is in line with the two-pronged approach of our current campaign , '' the statement said .

`` With this channel of communication finally opened , MEND will put together its ... team of frank negotiators to pass our demands and expectations to the president through Mr. Alaibe , a man we respect and can work with . ''

From CNN 's Christian Purefoy .

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Henry Okah , MEND 's main arms smuggler , was arrested in September 2007

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Okah is accused of treason , terrorism and kidnapping

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Lawyers , relatives say he needs kidney treatment not available in Nigeria